1. Field of the Invention
The present invention relates to an image forming apparatus for forming an image by an electrophotographic method or by an electrostatic recording method.
2. Description of the Related Art
As an image forming apparatus for forming an image by an electrophotographic method or by an electrostatic recording method, conventionally an image forming apparatus with a developing sleeve is often employed. In these methods, an electrostatic latent image formed on an image bearing member is developed using one-component developer or two-component developer
In general, the developing sleeve is rotatably supported on an opening of a developing device by bearings at both ends. In order that the developer is easily carried on the developing sleeve, the surface of the developing sleeve may be subjected to a roughening treatment or grooves may be provided on the surface of the developing sleeve.
When an amount of developer in the developing sleeve surface is not uniform, there is a possibility that a density of an image visualized on the photosensitive member becomes uneven. Therefore, it is desirable to make uniform an amount of developer on the developing sleeve surface. As a countermeasure of this problem, a regulating member, called “regulating blade” is generally used to uniformly regulate an amount of developer on the developing sleeve surface.
The developing device includes a developing container for containing developer, where a conveying member such as a screw or the like is generally disposed. The developer is circulated and conveyed in the developing container by the conveying member.
By the way, the phenomena may occur in the developing device, that a foreign matter is pinched between the regulating blade and the developing sleeve, agglomerates are coated as a toner layer grows due to deterioration of the developer, or agglomerates are clogged. In these cases, coated agglomerates are developed and thereby agglomeration marks appear or concentration of the developer becomes lower due to the fact that the coat of the developer becomes thinner in a region where the agglomerates are caught.
For this problem, in Japanese Patent Laid Open Publication No. H11-231645, a method of removing a caught foreign matter is proposed, wherein the regulating blade is moved to release it spatially. However, in this method, because the regulating blade is moved to release it spatially, the coating amount becomes more as compared with the normal period and thus it is difficult to perform this method during image forming operation. Also, if this method is carried out in a non-image formation period, the time period in which image formation is not performed becomes longer.
Therefore, in Japanese Patent Laid Open No. 2009-93073, a method of vibrating a layer thickness regulating blade during non-image formation period such as a post-rotation period after image formation and an inter-sheet interruption during image formation is proposed. This prevents image defects by minimizing downtime of the image formation and by avoiding growth of a toner layer.
However, in the method of vibrating a layer thickness regulating blade during non-image formation such as a post-rotation period after image formation and an inter-sheet interrupt during image formation as in the Japanese Patent Laid Open No. 2009-93073, toner agglomerates which come out by vibrating the regulating blade are leveled and return to the developing device. Since the toner agglomerates are degraded, if they return to the developing device, it may cause reduction of fluidity and degradation in development property.
The Japanese Patent Laid Open No. 2013-140273 discloses that the toner replacement control is performed, wherein when fluidity of the developer is reduced, an electrostatic latent image of 20% of image ratio in the post-rotation period and the electrostatic latent image is developed by the developing device and deteriorated toner is discharged. Furthermore, the Japanese Patent Laid Open No. 2013-140273 discloses a structure for recovering a stagnating state of the developer in the developer reservoir by vibrating a layer thickness regulating blade with a vibrator. It also discloses that the toner replacement control can be performed in parallel to blade vibration.
However, in the Japanese Patent Laid Open No. 2013-140273, the position to be vibrated by a blade is different from the position where the deteriorated toner is actually discharged to the photosensitive drum. Therefore, when the blade vibration is performed in parallel to the discharging operation, the toner having passed through the blade during vibration is not always discharged on a photosensitive drum. Therefore, there is a possibility that the deteriorated toner agglomerates passing through the blade during the blade vibration is collected in the developing device again without being discharged on the photosensitive drum.
Therefore, an object of the present invention is to suppress defects caused by the fact that the deteriorated toner agglomerates having passed through the regulating member are collected in the developing device when executing a mode for vibrating the toner agglomerates by driving the developer bearing member during a non-image formation period.